Fluorites

Amphiboles crystallize into two crystal systems, monoclinic and orthorhombic. Amphiboles are minerals of either igneous or metamorphic origin; in the former case occurring as constituents (hornblende) of igneous rocks, such as granite, diorite, andesite and others. Those of metamorphic origin include examples such as those developed in limestones by contact metamorphism (tremolite) and those formed by the alteration of other ferromagnesian minerals (hornblende). Pseudomorphs of amphibole after pyroxene are known as uralite.

The name amphibole (from the Greek word amphibolos meaning 'ambiguous') was used by René Just Haüy to include tremolite, actinolite, tourmaline and hornblende. The group was so named by Haüy in allusion to the protean variety, in composition and appearance, assumed by its minerals. This term has since been applied to the whole group. Four of the amphibole minerals are among the minerals commonly called asbestos. These are: Anthophyllite, Riebeckite, Cummingtonite/Grunerite series, and Actinolite/Tremolite series. The Cummingtonite/Grunerite series is often termed Amosite,or Brown Asbestos and Riebeckite is known as Crocidolite or Blue Asbestos. These are generally called Amphibole Asbestos.